Conventionally, many bubbling-type vaporization and supply apparatuses have been used as a raw material vaporization and supply apparatus by the MOCVD method for semiconductor manufacturing equipment. However, the bubbling method has a lot of problems in flow rate control of raw material gas to be supplied, concentration control of the raw material gas, and a vapor pressure of the raw material gas etc., and therefore, the inventors disclosed a vaporizer-type raw material vaporization and supply apparatus with a pressure-type flow rate control device for controlling a flow rate of raw material gas to solve the problems (Japanese Unexamined Patent Application Publication No. 2009-252760). In addition to the vaporizer-type raw material vaporization and supply apparatus, the inventors are developing a baking-type raw material vaporization and supply apparatus with a pressure-type flow rate control device for controlling a flow rate of raw material gas (Japanese Unexamined Patent Application Publication No. 2013-33782, Japanese Unexamined Patent Application Publication No. 2012-234860 etc).
FIG. 9 is a block diagram illustrating the vaporizer-type raw material vaporization and supply apparatus that has a raw material receiving tank T, a supply flow rate control device Q, a vaporizer 1, a high-temperature pressure-type flow rate control device 2, and a heating device 6 (6a, 6b, 6c etc.), and the vaporizer 1 and the high-temperature pressure-type flow rate control device 2 constitute an essential part of the raw material vaporization and supply apparatus. In FIG. 9, reference symbol M designates a heating temperature control device, reference symbol V1 designates a fluid supply flow rate control valve, reference symbol L designates a relief valve, reference symbol Gp designates gas for pressurizing the raw material receiving tank, reference symbol LG designates a raw material liquid, reference symbol G designates raw material gas, reference symbols T0 and T1 designate temperature detectors, reference symbols V2 to V7 designate opening-and-closing valves, reference symbols P0 and P1 designate pressure detectors, reference symbol 3 designates a vaporizing chamber, reference symbol 4 designates a pulsation reducing orifice, reference symbol 5 designates a liquid storing part, reference symbols 7 and 8 designate flow passages, and reference symbol 9 designates a buffer tank.
FIG. 10 is a perspective view of a longitudinal section of the vaporizer 1 shown in FIG. 9, and reference symbol 3d designates a raw material liquid inlet, reference symbols 3f and 3g designate heating promoters, reference symbol 3e designates a gas outlet, and reference symbol 4a designates a hole. FIG. 11 is a perspective view of a combined structure of the vaporizer 1 and the high-temperature pressure-type flow rate control device 2 shown in FIG. 9, and the high-temperature pressure-type flow rate control device 2 is mounted and fixed on top of the vaporizing chamber 3 that is surrounded by a heating board 11 with a heater 10. Here, reference symbol 2a designates a main body of the flow rate control device.
In the vaporizer 1 shown in FIG. 9, a supply flow rate of the liquid LG from the raw material receiving tank T is controlled by adjusting an internal pressure of the tank T and an opening degree of the fluid supply flow rate control valve V1 via the supply flow rate control device Q, and the supply flow rate of the liquid LG is controlled by a signal emitted from the pressure detector P0 located at an outlet side of the vaporizer 1 to have a gas pressure at an upstream side of the high-temperature pressure-type flow rate control device 2 be no lower than a predetermined pressure value. Similarly, input to a heater of the heating device 6a and control of the opening degree of the fluid supply flow rate control valve V1 are conducted via the heating temperature control device M by signals emitted from the heating temperature detector T0 of the vaporizer 1, and the gas pressure at the upstream side of the high-temperature pressure-type flow rate control device 2 is controlled to be no lower than the intended pressure value by the supply flow rate control device Q and the heating temperature control device M.
In the vaporizer-type raw material vaporization and supply apparatus, since raw material gas that is vaporized in the vaporizer 1 is controlled by the high-temperature pressure-type flow rate control device 2 that can stably control a flow rate, precision of flow rate control is not affected at all even a temperature or a pressure condition at a side of the vaporizer 1 slightly fluctuates. Therefore, even in a condition where precision of controls of the temperature and the pressure (flow-in rate of the liquid) at the side of the vaporizer 1 slightly lowers, precision of the flow rate control of the raw material gas G does not drop and highly precise gas flow rate control can be stably conducted.
There are more advantages available: an internal pressure of the vaporizing chamber 3 fluctuates less because the internal space of the vaporizing chamber 3 of the vaporizer 1 is divided into a plurality of areas by the pulsation reducing orifice 4; gas is stably supplied to the high-temperature pressure-type flow rate control device 2 because the internal space of the vaporizing chamber 3 serves as a buffer tank; liquid portion is stably vaporized by heating the vaporizing chamber 3 evenly; and recondensation of the gas in the flow rate control device main body 2a is perfectly prevented by keeping a temperature difference at a gas contact part in the high-temperature pressure-type flow rate control device 2 within about 6° C.
On the other hand, the baking-type raw material vaporization and supply apparatus that is currently under development by the inventors includes a raw material receiving tank T that stores a raw material liquid LG, a constant temperature heating device 12 that heats the raw material receiving tank T etc, and a pressure-type flow rate control device 2 that controls a flow rate of raw material gas G which is supplied from an internal upper space Ta of the raw material receiving tank T to a process chamber 13 as shown in a block diagram of FIG. 12. Here, in FIG. 12, reference symbol 14 designates a raw material liquid supply port, reference symbol 15 designates a purge gas supply port, reference symbol 16 designates a diluent gas supply port, reference symbol 17 designates a gas supply port for another thin-layer forming gas, reference symbols 18, 19, and 20 designate flow passages, and reference symbols V8 to V16 designate valves.
The raw material receiving tank T is filled with a moderate amount of the liquid raw material (such as an organic metal compound like TMGa) or a solid raw material (such as TMIn powder or an organic metal compound supported by a porous support body), and the raw material is heated by a heater in the constant temperature heating device 12 (not shown) to a temperature between 40° C. and 220° C. to fill the internal space Ta of the raw material receiving tank T with raw material vapor G0 of the raw material liquid LG or the solid raw material with a saturated vapor pressure which is generated at a reached temperature.
Then, the generated raw material vapor G0 flows into the pressure-type flow rate control device 2 through the raw material vapor outlet valve V9 and the raw material gas G of which flow rate is controlled by the pressure-type flow rate control device 2 to be a predetermined flow rate is supplied to the process chamber 13. Purge gas Gp such as N2 for purging flow passages of the raw material gas G or the like is supplied from the purge gas supply port 15 and diluent gas G1 such as helium, argon, or hydrogen is supplied from the diluent gas supply port 16 as needed. Since the flow passages for the raw material gas G is heated to a temperature between 40° C. and 220° C. by the constant temperature heating device 12, the raw material gas G is not recondensed.
FIG. 13 is a sectional view schematically illustrating an essential part of the baking-type raw material vaporization and supply apparatus, and the high-temperature pressure-type flow rate control device 2 is mounted and fixed on top of the raw material receiving tank T to lead the raw material vapor G0 in the raw material tank T directly to the high-temperature pressure-type flow rate control device 2 that controls a flow rate of the vapor and supplies it to the process chamber 13 (not shown).
For the baking-type raw material vaporization and supply apparatus, it is possible to supply the only pure raw material gas G to the process chamber 13 all the time and this allows a raw material vapor concentration to be controlled easily and highly precisely. Additionally, by using the high-temperature pressure-type flow rate control device 2, clogging due to condensation of the raw material gas G which is seen in use of a mass flow rate control device (thermal-type mass flow rate control device) is eliminated and more stable supply of the raw material gas G may be realized comparing to a raw material vaporization and supply apparatus with the thermal-type mass flow rate control device. Furthermore, there are more advantages available such as highly precise flow rate control even in a slight fluctuation of a vapor pressure of the raw material vapor G0 in the raw material receiving tank T and a major reduction in size as well as in production cost of the raw material vaporization and supply apparatus.
However, there are still a lot of problems to be solved left even in the vaporizer-type raw material vaporization and supply apparatus as well as the baking-type raw material vaporization and supply apparatus. Firstly, there is a problem about pyrolysis of the raw material gas G. Generally in a semiconductor processing apparatus, stable supply of the high purity raw material gas G with a higher vapor pressure is desired for preventing recondensation of process gas at some point in the pipelines or for processing efficiency. Specifically, the raw material gas G needs to be heated to a quite high temperature to generate a high vapor pressure like 200 kpa abs which is desired in some cases and, for example, a temperature to be heated to for obtaining the vapor pressure of 200 kPa abs and then to be maintained at is 200° C. in case the raw material gas is TEOS, 150° C. in case of TEB, 150° C. in case of TMIn, 140° C. in case of DEZn, and 160° C. in case of TiCl4.
However, there is a weak point that gases of some organic metal raw materials for semiconductor production are pyrolyzed below their boiling points by contacts with metal materials and therefore, not all the organic metal raw materials may be stably supplied.
Also, many component devices that constitute the raw material vaporization and supply apparatus include valve elements and/or sealants of various opening-and-closing valves made of a resin material that contact with the gas. However, whether contacts with those resin-made parts cause pyrolysises of the raw material gases and, in case pyrolysises are caused, then heating temperatures at which the raw material gases are pyrolyzed have not been investigated at all. This is the other remaining issue in stable supply of the organic metal raw material gases.
Of course, so-called passivation treatment techniques (Japanese Patent No. 4085012etc.) have been developed and widely used for inhibiting emission of particles from outer surfaces of metal-made passages as well as component devices and for preventing pyrolysises of process gases by controlling catalytic action of the outer metal surfaces. However, the conventional passivation techniques of this type are for pipelines and component devices used for gases at low temperatures below 100° C. to 120° C. and there is a problem remained that prevention effects of the passivation treatments on raw material gas pyrolysis etc. when applied to pipelines and component devices used for organic metal raw material gases at high temperatures over 150° C. have not been sufficiently analyzed.